Read and learn about the ice age and relict salmon
Two unique types of salmon in Norway don't do what other wild salmon do. While the others travel to the sea to eat their way to adulthood, these two stay at home - all their lives. Read the text below to find out why this has happened.
Competency goals for grade 7, Science
- explain how organisms can be divided into main groups and give examples of the characteristics of different organisms.
- explain the importance of biodiversity and implement measures to preserve biodiversity in the local environment.
- explain how the geological cycle, plate tectonics and external forces help to shape and change different landscapes.
During the last ice age, large parts of Europe were covered in ice.
Ice age, land uplift and wild salmon
There have been several ice ages. The most recent was a period between 110,000 and 10,000 years ago. At that time, large parts of Europe were covered in ice. This is how we can begin the story of wild salmon in Norway.
The country rose
At its peak, the ice was up to three kilometers thick. As the ice melted, rivers formed. Wild salmon in the sea quickly found these rivers and put them to use. When the heavy ice disappeared, the land began to rise. In some places, the land rose even more. Small and large waterfalls formed in the rivers. Some of the waterfalls were too high for even the fittest wild salmon. The wild salmon therefore had to find spawning grounds below the large waterfalls.
Strange things happen over four large waterfalls
Since salmon no longer returned to the areas above the large waterfalls, the wild salmon died out here. But over four large waterfalls in Norway, something strange happened. Even though no new wild salmon were returning from the sea, there were still wild salmon here. Here, both the female and male salmon that remained could reach sexual maturity without going to sea. Thus, spawning continued and the wild salmon lived on across the four large waterfalls.
Insulated salmon
Above the large waterfalls, they lived isolated from the sea-migrating salmon. Salmon populations that live like this are very rare. Since they remained in the wild salmon's old areas, we call them relict salmon stocks. The word relict means "something that remains".
Small wild salmon
Relict salmon belong to the same species as the sea-migrating salmon. Since relict salmon don't go to the sea, they have to make do with the food available in the river. It therefore does not grow very large. The picture shows an adult relict salmon.
Photo: Hans Mack Berger
Questions
Unfortunately, two of the four relict salmon have been wiped out. Now there are only two left. Search online and find out their names.
Where in Norway can we find them?
Find out how they are doing and if there is any threat to them.
Explain why you agree or disagree with this statement: "Since they don't grow very big, they are not particularly important to take care of". Discuss this in class.
For the teacher
To understand the story, you need to understand the life cycle of wild salmon. Wild salmon migrate from the river to the sea to feed and then return to the river to spawn. In Norway, we have two relict salmon populations: the Namsblanken and the byglandsbleka. These only live in freshwater and do not migrate to the sea.
To explain land uplift, you can use a piece of foam rubber that you squeeze together. As the pressure is released, it will expand. Cut profiles in the piece of foam rubber so that some peaks will appear when the pressure is released.
The assignment "Endangered relict salmon - about human impact" can be a nice review before you start discussing the statement in the assignment.
Student booklet
The Nasjonalt villakssenter works for a stronger wild salmon and wants to promote the stream as an educational resource. Bring experiences from the classroom and put them in context with experiences outside. Many schools in Norway have a local stream. Even in our largest cities, there are streams that can be visited. Contact us for assistance, tips and professional support.
The student booklet "Who lives in your river?" can help with both preparation and follow-up work.